1. Field of the Invention
The present invention relates to a mobile communication for carrying out multiple simultaneous communications using a plurality of independent calls on each mobile terminal device.
2. Description of the Background Art
As shown in FIG. 1, the conventional mobile communication system generally comprises a mobile terminal device 100 and a network device 101 which are connected through a communication channel 103. The mobile terminal device 100 and the network device 101 are provided with respective call control units 104 and 105 so that the call origination control and the call termination control are carried out by the call control units 104 and 105.
In such a conventional mobile communication system, a possibility of more than one simultaneous communications on a single mobile terminal device has not been taken into account, so that the communication state and the call state of the mobile terminal device are expected to be identical during the communication, and for this reason no function for managing the communication state of the mobile terminal device has been provided in either the mobile terminal device 100 or the network device 101.
Because of this lack of a function for managing the communication state of the mobile terminal device, it has been impossible in the conventional mobile communication system to ascertain the correspondences between the call control unit 104 of the mobile terminal device 100 and the call control unit 105 of the network device 101.
As a consequence, if more than one simultaneous communications are attempted On a single mobile terminal device by simply providing additional transmission and reception devices and using the conventional call management scheme, there arises a problem that the network device 101 would carry out the unnecessary paging operation when the subsequent call is terminated at that mobile terminal device, despite of the fact that the network device 101 already ascertained the channel connection target from the earlier communication.
In addition, there is also a problem that it has been impossible to collectively control all or a part of the call states on the mobile terminal device 100.